Pen-type injector

Abstract

The present invention relates to injectors, such as pen-type injectors, that provide for administration of medicinal products from a multidose cartridge and permit a user to set a delivery dose. An injector may include a housing, the cartridge containing a medicinal product, the cartridge being retained within the housing, a dose dial sleeve for selecting a dose of the medicinal product to be expelled, and a piston rod for expelling the selected dose of the medicinal product. The housing may be a unitary housing within which the dose dial sleeve for selecting the dose and the piston rod for expelling the selected dose are moveably retained. Alternatively, the injector may include the housing, the piston rod, an insert located in the housing and through which the piston rod may rotate, a ratchet, the dose dial sleeve, a drive sleeve, a button located on the drive sleeve and rotatable with respect to the drive sleeve, and a clutch which upon depression of the button prevents rotation between the dose dial sleeve and the drive sleeve.

The invention claimed is: 
     
       1. A drug delivery device, comprising:
 a housing; 
 a dose dial sleeve provided with a plurality of teeth on an internal surface; 
 a drive sleeve carrying a toothed member configured to ride over the plurality of teeth of the dose dial sleeve; 
 a piston rod coupled to the drive sleeve; 
 a ratchet configured to prevent rotation of the piston rod during dose selection and that the piston rod in turn prevents rotation of the drive sleeve during the dose selection; and 
 a nut located between the drive sleeve and the dose dial sleeve, where the nut moves axially relative to the housing during the dose selection, 
 wherein the drive sleeve is prevented from rotating with the dose dial sleeve during the dose selection and the dose dial sleeve rotates together with the drive sleeve during dose delivery. 
 
     
     
       2. The drug delivery device according to  claim 1 , wherein relative rotation between the dose dial sleeve and the drive sleeve will cause the toothed member to ride over the plurality of teeth of the dose dial sleeve. 
     
     
       3. The drug delivery device according to  claim 1 , further comprising a button, wherein
 when the button is pressed, the drive sleeve is driven into the dose dial sleeve to prevent relative rotation between the dose dial sleeve and the drive sleeve. 
 
     
     
       4. The drug delivery device according to  claim 1 , wherein the piston rod is configured to advance during the dose delivery until the drive sleeve and the dose dial sleeve have returned to an initial position. 
     
     
       5. The drug delivery device according to  claim 4 , wherein the piston rod has a screw thread. 
     
     
       6. The drug delivery device according to  claim 1 , comprising a medicinal product in a cartridge. 
     
     
       7. The drug delivery device according to  claim 6 , where an axial position of the nut after the movement of the nut during the dose selection corresponds to an amount of the medicinal product remaining in the cartridge. 
     
     
       8. The drug delivery device according to  claim 1 , wherein an outer surface of the dose dial sleeve includes graphics and wherein the housing is provided with an aperture or a window through which a portion of the graphics may be viewed. 
     
     
       9. The drug delivery device according to  claim 1 , wherein the dose dial sleeve comprises a first cylindrical portion rigidly connected to a second cylindrical portion. 
     
     
       10. The drug delivery device according to  claim 1 , wherein the axial movement of the nut is prevented during the dose selection when a user of the drug delivery device attempts to set a dose greater than an amount of a medicinal product remaining in the drug delivery device.